Ultra-Shallow Boron Doping via Solid Phase Diffusion
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Solution Overview
Problem
The semiconductor industry faces challenges in forming ultra-shallow dopant regions with uniform doping profiles and high surface concentration, particularly in complex device structures like FinFETs and recessed channel transistors, due to limitations in ion implantation techniques which result in lattice damage and non-uniform doping.
Innovation Solution
The method involves depositing a boron dopant layer using atomic layer deposition (ALD) with an oxide, nitride, or oxynitride on the substrate, patterning it, and then diffusing boron through thermal treatment to form ultra-shallow dopant regions, allowing for conformal doping in planar, raised, or recessed features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to form shallow junctions, then dopant atoms can be driven into the substrate, but the path of energized dopant atoms and implant uniformity become difficult to control at low energies
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical deposition process (CVD or ALD) to form a dopant-containing dielectric layer. This substitution eliminates the need to accelerate ions and control their path through the substrate, thereby resolving the uniformity and control issues inherent in ion implantation at low energies.
Solution Approach 2:
The patent changes the fundamental parameter of dopant introduction from high-energy physical implantation to low-energy chemical deposition followed by thermal diffusion. This parameter change allows precise control of junction depth through diffusion time and temperature, achieving uniform doping profiles that were difficult to obtain with ion implantation.
2Ease of manufacture
If high energy dopant atoms are implanted into the substrate, then dopant regions can be formed, but the crystal lattice is damaged and dislocations spike across shallow junctions causing current leakage
Solution Approach 1:
The patent replaces the mechanical bombardment of ion implantation with a chemical deposition process. The dopant-containing dielectric layer is formed using CVD or ALD, which deposits material without damaging the crystal lattice. Subsequent thermal diffusion gently introduces dopants without the high-energy impact that causes lattice damage and dislocation formation.
3Quantity of substance
If p-type dopants such as boron are implanted, then dopant regions can be formed, but excessive dispersion of dopant atoms occurs after introduction into the substrate
Solution Approach 1:
The patent replaces ion implantation with chemical deposition of a dopant-containing dielectric layer followed by thermal diffusion. This approach allows precise spatial confinement of the dopant source within the dielectric layer, and the thermal diffusion process provides controlled, uniform dopant distribution without the excessive dispersion caused by ion implantation.
Solution Approach 2:
The patent performs preliminary action by forming the dopant-containing dielectric layer in a controlled manner before diffusion. The dielectric layer is deposited with precise thickness and composition control using CVD or ALD, and dopant precursors are incorporated during deposition. This preliminary preparation ensures uniform dopant distribution and prevents excessive dispersion during the subsequent diffusion process.
4Manufacturing precision
If ion implantation is used for conformal doping of 3D structures, then line of site doping can be achieved, but special substrate orientations are required and shadowing effects prevent uniform doping at high device densities
Solution Approach 1:
The patent replaces the directional, line-of-sight ion implantation process with conformal chemical vapor deposition or atomic layer deposition. These deposition methods deposit material conformally on all surfaces of 3D structures regardless of orientation, eliminating shadowing effects and the need for specific substrate orientations. The dopant-containing dielectric layer is formed uniformly on vertical, horizontal, and recessed surfaces.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the formation of highly confined, ultra-shallow boron dopant regions with improved uniformity and reduced lattice damage, suitable for advanced semiconductor devices, overcoming the limitations of conventional ion implantation methods.
Implementation Method 1
depositing, by atomic layer deposition (ALD), a boron dopant layer in direct contact with the substrate, the boron dopant layer containing an oxide, a nitride, or an oxynitride
Implementation Method 2
forming the ultra-shallow boron dopant region in the substrate by diffusing boron from the patterned boron dopant layer into the substrate by a thermal treatment
Implementation Method 3
forming the ultra-shallow boron dopant region in the substrate by diffusing boron from the patterned boron dopant layer into the substrate by a thermal treatment
Data Source
AI summary
A method for forming an ultra-shallow boron dopant region in a substrate is provided. In one embodiment, the method includes depositing, by atomic layer deposition (ALD), a boron dopant layer in direct contact with the substrate, where the boron dopant layer contains an oxide, a nitride, or an oxynitride formed by alternating gaseous exposures of a boron amide precursor and a reactant gas. The method further includes patterning the dopant layer and forming an ultra-shallow dopant region in the substrate by diffusing boron from the boron dopant layer into the substrate by a thermal treatment.